In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals 5300 < Teff < 7300 K, logg > 4 (cgs) and 0.3 < (B- V) 0 < 0.8 mag, respectively. Stars with relative trigonometric parallax errors sp/p = 0.01 were preferred from Gaia DR2 data for the estimation of their MV absolute magnitudes. In order to obtain calibrations, (U - B) 0 and (B - V) 0 colour indices of stars were preferred and a multi-variable second order equation was used. Calibrations are valid for main-sequence stars in the metallicity and absolute magnitude ranges -2 < [Fe/H] < 0.5 dex and 2.5 < MV < 6 mag, respectively. The mean value and standard deviation of the differences between original and estimated values for the metal abundance and absolute magnitude are [Fe/H] = 0.00 +/- 0.11 dex and MV = 0.00 +/- 0.22 mag, respectively. In this work, it has been shown that more precise iron abundance and absolute magnitude values were obtained with the new calibrations, compared to previous calibrations in the literature.